crowther



H. M. CROWTHER.

, SPARK PLUG. APPL'ICATION FILED HIL? I5. |918,

` Patentd Aug. 26,1919.

III

INVEN ron Y HENRY M. Caowr/m? 3, /J/. 11 Alsl A r r'vs.

HENRY M. CBOWTHER, 0F KING-MAN, ARIZONA.

SPARK-PLUG.

Specification of Letters Patent.

Patented Aug. 26, 1919.

Application led July 15, 1918. Serial No. 245,034.

To all whom it may concern:

Be it known that I, HENRY M. Cnow'rrriin, a citizen of the United Statesresiding at Kingman, in the county of Mohave and State of Arizona, haveinvented new and useful Improvements in Spark- Plugs, of which thefollowing is a specification.

My object is to make a self-cleaning spark plug and my inventionconsists of the novel features herein shown, described and claimed.

Figure 1 is a vertical central sectional detail of a self-cleaning sparkplug embodying the principles of my invention.

Fig. 2 is a bottom plan view looking in the direction indicated by thearrow 2 in Fig. 1.

Fig. 3 is a perspective of the heater serving asa return terminal.

The insulating core 1 is preferably formed of porcelain or other strong,har refractory, non conducting material, and comprises the upper(fzylindrical portion 2, the annularretainintg ange 3 extending aroundthe lower end o the upper cylindrical portion 2, the lower cylindricalportion 4 extending downwardly from the annular .retaining ilange 3;said portions 2 and 4 being substantialll the same diameter; the reducedcylin rical portion 5 extending downwardly from the cylindrical portion4 and havin a rounded lower end 6 and an enlarge central bore 7 and ashoulder 8 at the top of the central bore 7, and the clrcular taperedshank 9 extending upwardly trom the upper cylindrical portion 2; therebeing a central bearing` bore 10 extending from the shoulder 8 upwardlythrough the lower c lindrical portion 4, the retainin ange 3, t e uppercylindrical portion 2 an the tapered shank 9, and there being a flatupper face 11 at the upper end of the shank 9.

The conductor feed rod 12 is inserted upwardly through the enlarged bore7 and through the bearing bore 10 and lits the bore 10; there being achamber 13 around the rod 12in the bore 7 and there being a stop 14fixed upon the rod to engage the shoulder 8 and hold the rod so that thelower end 15 will proj ect slightly beyond the rounded end 6.

A cap 16 ts against the flat face 11 and around the upper end of thetapered shank 9 and has a central opening through which the rod 12extends. A bindin post nut 17 is screwed upon the upper en of the rod-12 against the cap 16 to draw the stop 14 against the shoulder 8 andhold the parts tight. A second binding post nut 18 is screwed upon therod 12 against the first nut 17 and serves as a jam-nut, said secondbiliding post nut having a neck 19 to receive the feed conductor.

The heater 20 is preferably stamped from good sheet copper and comprisesa cylindrical portion 21 slightl larger in diameter than the lower cylinrical portion 4, the flaring retaining flange 22 extending from theupper edge of the cylindrical portion 21, the cy indrical foraminousportion 23 extending downwardly from the portion 21, and the roundedforaminous ortion 24 extending downwardly froin t e portion 23 andhaving a central circular opening 25. A cushion 26 of asbestos paper orthe like is placed around the lower cylindrical portioin 4 of theinsulating core, a similar cushion 27 is placed against the inclinedlower face 28 of the retaining liange 3, and the heater 20 is insertedupwardly around the cushion 26 against the cushion 27; there being achamber 29 within the heater around the reduced cylindrical portion 5and an extension chamber 30 within the heater around the rounded lowerend 6 of the insulating core, and the lower end 15 of the conductor feedrod 12 bein centrally located in the opening 25, sai lower end 15serving as the' feed terminal of the spark gap 31, and the edge of theheater around the opening 25 serving as the return terminal for t espark gap.

The metal case 32 has a hexagonal upper end 33 forming a wrench seat andsaid upper end has an internal screw-thread 34. An externallyscrew-threaded nipple 35 extends downwardly from the upper end 33, saidnipple being reduced in size relative to the upper end 33 and thethreads 36 upon the nipple being adapted for screwing into the head ofthe engine cylinder. An internal inclined shoulder 37 is formed at thebottom of the threads 34 and a bore 38 extends through the nipple 35 tothe shoulder 37. The metal case 32 is inserted upwardly around theheater 20, the cylindrical portion 21 0f the heater iitting tightly inthe bore 38, and the flange 22 fitting closely against the shoulder 37.The lower end of the bore 38 is enlarged to form the chamber 39 aroundthe foraminous portion 23 within the lower `end of the nipple 35.

A cushion 40 of asbestos paper or the like is placed around the uppercylindrical portion 2 and a similarpacking 41 is placed against theupper face of the flan e 3, and a gland 42 is screwed down into tiethreads 34 around the cushion 40 and against the cushion 41 to draw thecasing 32 tightly against the cushion 27 and hold the parts together. Ahexagon head 43 forms a Wrench seat upon the upper end of the gland 42.

The trouble with the best spark plugs heretofore made hasbeen that theinsulating cores will become coated with smoke, lamp black, or carbon,from poor combustion of the explosive mixture, and this coating formsmore or less of an electric conductor to carry theelectricity from thecentral feed rod along the surface of the insulating core to the casing.In this type of spark plugs the casing forms the return side of thespark gap. In order that a spark plug shall Work satisfactorily it isnecessary that the entire force of the electric current pass through thespark gap and any leakage of the current duc to the smoke deposit uponthe insulatin core will reduce the Vpower and certainty of the spark. Itis not necessary that a full short circuit be established between the fdrod and the casing to ruin the efliciency of the spark plug. Anycontinuous layer of soot or smoke or carbon, all of which may be calledlamp black, extending from the feed rod 12 along the 'exposed face ofthe insulating core l to the casing 32 reduces the efficiency of thespark to the extent of the current Which Will leak through this layeroflanip black, and any effective gap or breakin this layer of lamp blackvvi'l'l stop the leak, although the other parts may be loaded with lampblack.A

v"While the heater 20 serves as the return side ofthe spark gap, theobject of the particular construction shovvnand described is to burnthelamp black from the' exposed face of the insulatin core and break thecircuit of electricity t rough the lamp black from the feedI rod 12tothe casing 3 The chambers 29 and 30 are substantially of eventhickness between the heater 20 andV the face of the insulatin core. Thematerial of the heater 20 arou'n these chambers is exposed to the flashof the exploding fuel mixture in the 'engine and this material should beof high`degree of fusibility soithat Will stand a temperature risingtothe verge "of red-hotness or incandescence for an indefinite time, andthe material should be of high'conductivity, absorption and radiation sothat it will readily become heated to vth'erdeslred extent and readilygive off the heat to lower theteinperature so that at'thetime 'of theexplG'Sive flash the heater Will be almost or quite 'red-hot and. lwillretain this 'temperature for an instant andthen cool sliilicie'ntly sothat it' will not ign-imite next narge.

The explosive mixture Will enter the chambers 29 and v3() and at thetime of the explosion there will be a flash inside of the heater as Wellas outside and the heat will circulate freely through the opening 25 andthrough the perforations in theforaminous portions 23 and 24 and at thetime of the explosion and immediately following the explosion the heaterWill be hot enough to urn the lamp black from the surface of theportions 5 and 6 of the insulatin core. At this time the lamp black isbacks by the rc fractory,V non-heat-conducting, non-heat-absorbinginsulating core Iand is faced by an clement of high conductivity, hiabsorption, and rapid radiation, and t e heat of this element, theheater 20, in close prox imity to the lamp black; the lam black being aperfect absorber of heat; W1 linstantly ignite and burn the lamp black,thereby keeping the insulating core clean around the lower end of thebore 7, thereby making a break in the lamp black coating and preventinga short circuit or leakage of the electric current.

At the present time I consider copper the best medium for the heater 20.The lower end of the heater may be erforated more" or less as desired.The'thic' ness of the copper may be varied to some extent but I considerthat it should be comparatively thin so that it Ywill readily heat andso that the temperature will uctuate rapidly as the engine operates.

The heater 20 presents a very large surface both inside and out forcontact with the flash and the absorption of heat.

The lamp black deposit upon the inner and outer surfaces of the heaterduringthe period of poor combustion will ignite and burn whenthecombustion improves and the burning of this lamp black 'will assistin heatingi the heater and assist in burning the lamp b ack from theinsulating core.

T e layer of lam black as deposited is porous'and more or less saturatedwithoxyen and whileit will not ignite and burn rom theii'ash oftheexplosion it will read` ily burn in the presence of a hot element wherethe heat continues for a short time after the flash has gone. Theelement of time seems to be necessary to the burning ofI the lamp black.l V

Various changes may be made in the details of construction withoutdeparting from the spirit of my invention as claimed.

Iclaim: l I

1.' The'combination with a spark lug, of means entirely inclosing theexposedp end of the insulatin core for `breaking thecontinutyrdffthe ampbiack epositfonfthe insulating'cierre` j,

2. 'l hecomliination with a spark plug, :of heat absorbing andradiatin'gmeans `entirely inclosingthe exposed end ofthe insulating core forbreaking the continuity of the lamp black deposit on the insulatingcore.

3. The combination with a spark plug, of a heater entirely inclosing theexposed end of the insulating core and 1n position to burn the lampblack from the insulating core.

4. The combination with a spark plug, of an element entirely inclosingthe exposed end of the insulating core and in position to be heated bythe explosive flash and in position to burn the lamp black from theinsulating core to break the continuity of the lamp black deposit.

5. The combination with a spark plug having an insulating core, a feedrod extending through the insulating core, and a casing for mounting theinsulating core, of an element entirely inclosing the exposed end of theinsulating core and in position to be heat-- ed by the explosive flashand in position to burn the lamp black from the exposed inner end of theinsulating core.

6. The combination with a spark plu having an insulating core, a feedrod exten ing through the insulating core, and a casing for mounting theinsulating core, of a heater connected to the casing and entirelysurrounding the exposed inner end of the insulating core and forming thereturn side of the spark gap; said heater being adapted to burn the lampblack deposit to break the continuity thereof.

7. The combination with a spark plug having an insulating core, a feedrod extending through the insulating core and forming one side of thespark gap, and a casing for mounting the insulating core, of a heaterconnected to the casing and entirely surrounding the exposed inner endof the insulating core and formin the other side of the spark gap; saidheatergbeing spaced from the insulating core and being adapted toabsorb, conduct and radiate heat from the flash of the explosion to burnand break the continuity of the lamp black deposit upon the insulatingcore.

8. A spark plug comprising a cylindrical non-conductor having a reducedlower portion terminating in a semi-spherical head, a circular retainingflange intermediate its length and integral therewith, an innerconductor passing through the axis of the nonconductor, an outerconductor comprising a thimble shaped perforated thin shell, said shellbeing a good thermal conductor, said shell having a circular end flange,means for locking said ilange in position against said retainingflange,` said shell being perforated at its lower end and being slightlyspaced in parallel relation from the non-conductor, there being a sparkgap formed by an aperture at the center of the lower end of said shellthrough which the inner conductor projects.

9. A spark plug comprising an inner and an ,outer conductor, anon-conductor interposed therebetween, said non-conductor having acylindrical lower portion terminating in a semi-spherical head, theouter conductor comprising a perforated thin shell of metal, said shellbeing a good thermal conductor and slightly spaced in parallel relationfrom the non-conductor and provided with a spark gap consisting of anaperture at the apex of the shell through which the inner conductorprojects.

10. A spark plug comprising an inner and an outer conductor, anon-conductor interposed therebetween, said non-conductor having a lowerportion terminating in a head, the outer conductor comprising aperforated thin shell of metal, said shell being a goed thermalconductor and slightly spaced in parallel relation from the nonconductorand provided with a spark gap consisting of an aperture at the apex ofthe shell through which the inner conductor projects.

In testimony whereof I have signed my name to this specification.

HENRY M. CROWTHER.

Copies of this patent may be obtained for ve cents each, by addressingthe Commissioner of Patents, Washington, D. C.

